On-Off入力を用いた宇宙機の非線形姿勢制御へのMPCの適用に関する研究

　本研究では宇宙機の非線形運動とアクチュエータが持つ非線形オンオフ特性を考慮した閉ループの最適化安定化の問題を考える．そしてこの問題の解法として入力拘束を陽に考慮することのできるモデル予測制御(MPC) を用いる．MCP を用いた宇宙機の姿勢制御に関する研究はこれまでにも行われているが，アクチュエータとモデルの非線形性を同時に考慮したMPC の実用的な議論はなされていない．これらを用いる上での課題として，非線形性を含めた安定性，量子化入力による最適化，計算負荷の低減などがある．　1 章では本稿の背景・目的を，2 章で基礎的な安定性の性質についてまとめ本研究における問題設定を述べる．3 章では基本的なレギュレーション問題について上記の問題を解決できることを述べ，シミュレーションにより数値検証を行う．はじめにモデルと入力の非線形性を考慮した閉ループの安定条件を導出する．この安定条件は線形行列不等式(LMI) で与えられ，凸可解問題として容易に計算することが可能となる．数値シミュレーションでは複数のスラスタで構成されるリアクションコントロールシステム(RCS：reaction control system) のみを用いた制御を考える．アルゴリズムとしては分枝限定法を用いたオンオフ入力による非線形MPC の最適化を行う．これによって閉ループ系はISS とはなるが漸近安定にはならないこと，RCS とリアクションホイール(RW：reaction wheel) を併用して漸近安定化が可能であることを示す．　4 章では，これを拡張して，宇宙機が与えられた軌道を追従するトラッキング問題を考える．このとき，宇宙機の運動は目標軌道との誤差モデルとして記述することが可能である．この誤差モデルは非線形時変モデルとなるが，目標軌道回りで線形化を施せばLPV モデルとして記述することが可能である．ここでは，LPVモデルを設計に用いた最適化法と安定条件を求める．そして，こうして得られたトラッキング制御則をRCS で実装するためにパルス幅変調(PWM：pulse width modulation) を適用し，オンオフ入力による閉ループの安定性について議論する．　5 章は本論文のまとめであり，非線形性を考慮した宇宙機の姿勢制御問題についてのまとめと今後の展望について記述する．電気通信大学201

Ultra-Lightweight Deployable Antenna Membrane Technology for Future Non-terrestrial 6G Network and Earth Observation

A deployable antenna membrane is one of the promising solutions to achieve a higher speed of satellite communication and earth observation in small satellites. Unlike conventional deployable antennas, the proposed approach permits low flatness of the antenna membrane and compensates it electrically. By eliminating the conventional large deployment and support structure, the proposed non-planar membrane can be lighter and installed in small satellites. We introduce two types of membrane antennas: reflectarray antennas and active phased-array transceivers

Up-To-Date Magnetic Resonance Imaging Findings for the Diagnosis of Hypothalamic and Pituitary Tumors

Magnetic resonance imaging (MRI) is the preferred imaging technique for the sellar and parasellar regions. In this review article, we report our clinical experience with MRI for hypothalamic and pituitary lesions, such as pituitary adenomas, craniopharyngiomas, Rathke cleft cysts, germinoma, and hypophysitis with reference to the histopathological findings through a review of the literature. Our previous study indicated that three dimensional-spoiled gradient echo sequence is a more suitable sequence for evaluating sellar lesions on postcontrast T1 weighted image (WI). This image demonstrates the defined relationship between the tumor and its surroundings, such as the normal pituitary gland, cavernous sinus, and optic pathway. We demonstrated the characteristic MRI findings of functioning pituitary adenoma. In growth hormone-producing adenoma, signal intensity on T2WI is important to differentiate densely from sparsely granulated somatotroph adenomas. In prolactin-producing pituitary adenomas, distinct hypointense areas in early phase on T2WI, possibly owning to diffuse hemorrhage, indicate pronounced regressions of invasive macroprolactinomas during cabergoline therapy. The two histopathological subtypes, adamantinomatous and squamous papillary craniopharyngioma, differ in genesis. Calcified tumors are mostly adamantinomatous type. On MRI, these lesions have a heterogenous appearance with a solid portion and cystic components. The solid portions and cyst wall enhance heterogeneously. Although cyst fluid of Rathke cleft cysts show variable intensities on MRI, intracystic waxy nodule can be hypointense on T2WI. The enhancing cyst wall may contain the squamous metaplasia. Cystic lesions of the sellar and parasellar areas may be difficult to differentiate on a clinical, imaging, or even histopathological basis

Hybrid ubiquinone: novel inhibitor of mitochondrial complex I

AbstractWe synthesized novel ubiquinone analogs by hybridizing the natural ubiquinone ring (2,3-dimethoxy-5-methyl-1,4-benzoquinone) and hydrophobic phenoxybenzamide unit, and named them hybrid ubiquinones (HUs). The HUs worked as electron transfer substrates with bovine heart mitochondrial succinate–ubiquinone oxidoreductase (complex II) and ubiquinol–cytochrome c oxidoreductase (complex III), but not with NADH–ubiquinone oxidoreductase (complex I). With complex I, they acted as inhibitors in a noncompetitive manner against exogenous short-chain ubiquinones irrespective of the presence of the natural ubiquinone ring. Elongation of the distance between the ubiquinone ring and the phenoxybenzamide unit did not recover the electron accepting activity. The structure/activity study showed that high structural specificity of the phenoxybenzamide moiety is required to act as a potent inhibitor of complex I. These findings indicate that binding of the HUs to complex I is mainly decided by some specific interaction of the phenoxybenzamide moiety with the enzyme. It is of interest that an analogous bulky and hydrophobic substructure can be commonly found in recently registered synthetic pesticides the action site of which is mitochondrial complex I

High-grade Glioma Masquerading as a Small Cerebral Hemorrhage: A Case Report

We report a rare case of a high-grade glioma masquerading as a small subcortical hemorrhage. A 71-year-old woman came to a local hospital with sudden right upper extremity numbness. Computed tomography revealed a small subcortical hemorrhage with faint perifocal edema in the left postcentral gyrus. Conservative treatment was initiated, and she was discharged from the hospital with no neurological deficits. Six months later after discharge, she suffered an acute partial seizure of the right upper extremity. Magnetic resonance imaging with gadolinium demonstrated a ring-enhancing mass surrounded by severe perifocal edema in the hemorrhagic scar. We performed complete resection of the tumor, and the histological diagnosis was anaplastic oligodendroglioma. The diagnosis of a high-grade glioma was delayed due to intratumoral hemorrhages mimicking a small subcortical hemorrhage; consequently, we suspected the hemorrhage was induced by cerebral amyloid angiopathy. It may be important to repeat radiological follow up, if necessary, and to maintain clinical observance of possible intracranial neoplasm, even when the hemorrhage is small, particularly when the cause of bleeding is unknown